The subject matter disclosed herein relates generally to systems and methods for manufacturing ultrasound transducers, and more particularly to systems and methods for manufacturing and poling piezoelectric ceramic ultrasound transducers.
Ultrasound transducers perform ultrasonic examinations of a subject or sample (e.g., a patient or internal tissues of a patient) during which ultrasonic signals are converted to electrical signals, and vice versa. Ultrasound transducers, all or a portion of which may be housed within a probe, comprise, among other things, acoustic elements which transmit and receive the ultrasound signals. By way of receipt of ultrasound signals, the acoustic elements generate an image of the examined object. The number of acoustic elements in an ultrasound transducer may vary, as may their arrangement (e.g., matrix or linear arrays) and operation (e.g., sequential or phased operation).
At least some known ultrasound transducers utilize piezoelectricity. As is generally known, piezoelectricity is electricity generated by mechanical stress. Piezoelectric transducers comprise a piezoelectric component, in which transduction between mechanical stress and electricity may occur. Certain ceramics, such as lead zirconate titanate (PZT), for example, provide for exemplary piezoelectric components. Resultantly, piezoelectric ceramic transducers are used in a wide range of disciplines which utilize piezoelectric transduction, including medical instrumentation.
During manufacturing of piezoelectric ceramic transducers, piezoelectric ceramic components must be poled prior to use in a transducer. Poling of piezoelectric ceramic components is necessary to align the dipoles within the piezoelectric ceramic component. In a natural state, dipoles within the piezoelectric ceramic component are randomly arranged. Rearranging said dipoles into a polarized orientation is necessary for the piezoelectric component, and thus the transducer, to consistently and effectively transfer electrical and ultrasonic signals. Failure to sufficiently pole the piezoelectric ceramic component results in inferior or unusable ultrasound images, or may prohibit the transducer's use in an ultrasonic imaging device all together.
Piezoelectric ceramic components are commonly poled by manually or physically contacting each acoustic element with an electrode. Contact poling has significant drawbacks, however. For instance, contact poling provides for a relatively high likelihood of inconsistent or ineffectual poling due to manual or machine error in failing to contact each transducer element with the electrode. Some transducers, comprising thousands of acoustic elements and/or large acoustic stacks, make contact poling a highly labor-intensive, laborious process. Moreover, transducers with high numbers of acoustic elements (e.g., 5,000-10,000) require many points of contact by the electrode. As more points of contact are required, the likelihood of failing to contact each element increases, as does the likelihood of damaging the acoustic elements during contact.
Another disadvantage of contact poling is the effect of electrical shorts on the contact-poling process. If an acoustic element is shorted to a ground, for instance, the voltage provided by the poling electrode will not traverse the element to pole the element. Such shorting of one element may also affect other elements, resulting in a multiplication of the number of elements which were not poled.